1. Field of the Invention
This invention is directed generally towards digital image processing and more specifically towards generation and use of an improved device profile for describing both spatial and color properties of a device within an image processing system, so that a processed image can be more accurately captured, transformed or rendered.
2. Description of the Prior Art
Digital image processing involves electronically capturing an image of a scene, altering the captured image in some desired fashion and passing the altered image to an output device. An upstream element of a digital image processing system can be thought of as a source device, whereas a downstream element can be thought of as a destination device. For instance, a simple image processing system could include an acquisition device such as a digital camera, camcorder, scanner, CCD, etc., a color processor for processing the colors of the image, and an output device, such as a printer, monitor, computer memory, etc. When considering a communication between the acquisition device and the color processor, the acquisition device is deemed as the source device whereas the color processor is deemed as the destination device. When considering a communication between the color processor and the output device, the color processor is deemed as the source device whereas the output device is deemed as the destination device.
All imaging devices, either image acquisition or image display, will impose distortions of the color and spatial components of the image data.
Historically, industry has chosen to correct these distortions with device dependent solutions. It is common practice in the industry that an integral part of the design and calibration of such devices is the characterization of these distortions in the image data and modifications of the design of the devices to ameliorate these distortions. For example, electronic peaking filters are often employed in video capture devices to correct for the blurring effects of anti-aliasing filters and amplifier frequency response. Electronic imaging devices are commonly designed to function with specific upstream (in the case of display devices) or downstream (in the case of image sources) devices to provide quality images. For example, image capture devices commonly transform the image digits to compensate (`gamma corrected`) for the CRT volts-luminance characteristics of CRT displays. Such design considerations provide a device dependent model for that specific implementation of an image processing system, but do not provide the same degree of image quality when substituting an alternative device.
Recently, device independent paradigms for the characterization of color information in an image processing system have been developed and are being implemented: Color Sync, developed by Apple Computer and KCMS, developed by Eastman Kodak Co., are examples of systems or components supporting a device independent color paradigm. This paradigm is based upon a characterization of the image pixel data (digits) in a device independent color space--e.g. CIE L*a*b* or CIE XYZ, and the use of a Color Management System. The characterization of a device's image pixel data in device independent color space is commonly codified in a tagged file structure, referred to as a device profile, that accompanies the digital imaging device. However, the spatial characteristics of digital imaging devices are still modified in the context of the device dependent model described above.
In order to improve processing flexibility and versatility, it is a primary object of the present invention to apply a device independent paradigm to spatial processing in a digital image processing system. This paradigm will capture the spatial characterization of the imaging device in a tagged file format, referred to as a device spatial profile.